This invention relates to a process for polymerizing propylene in the presence of a catalyst system which comprises an activator and a [1,2-b]indenoindolyl Group, 4-6 transition metal complex having open architecture.
While Ziegler-Natta catalysts are a mainstay for polyolefin manufacture, single-site (metallocene and non-metallocene) catalysts represent the industry""s future. These catalysts are often more reactive than Ziegler-Natta catalysts, and they produce polymers with improved physical properties. The improved properties include narrow molecular weight distribution, reduced low molecular weight extractables, enhanced incorporation of xcex1-olefin comonomers, lower polymer density, controlled content and distribution of long-chain branching, and modified melt rheology and relaxation characteristics.
Single-site olefin polymerization catalysts having xe2x80x9copen architecturexe2x80x9d are generally known. Examples include the so-called xe2x80x9cconstrained geometryxe2x80x9d catalysts developed by scientists at Dow Chemical Company (see, e.g., U.S. Pat. No. 5,064,802), which have been used to produce a variety of polyolefins. xe2x80x9cOpen architecturexe2x80x9d catalysts differ structurally from ordinary bridged metallocenes, which have a bridged pair of pi-electron donors. In open architecture catalysts, only one group of the bridged ligand donates pi electrons to the metal; the other group is sigma bonded to the metal. An advantage of this type of bridging is thought to be a more open or exposed locus for olefin complexation and chain propagation when the complex becomes catalytically active. Simple examples of complexes with open architecture are tert-butylamido(cyclopentadienyl)dimethylsilyl-zirconium dichloride and methylamido(cyclopentadienyl)-1,2-ethanediyl-titanium dimethyl: 
Organometallic complexes that incorporate xe2x80x9cindenoindolylxe2x80x9d ligands are known (see U.S. Pat. No. 6,232,260 and PCT Int. Appl. WO 99/24446 (xe2x80x9cNifant""evxe2x80x9d)). The ""260 patent demonstrates the use of non-bridged bis(indenoindolyl) complexes for making HDPE in a slurry polymerization. Versatility is an advantage of the complexes; by modifying the starting materials, a wide variety of indenoindolyl complexes can be prepared. xe2x80x9cOpen architecturexe2x80x9d complexes are neither prepared nor specifically discussed. Nifant""ev teaches the use of bridged indenoindolyl complexes as catalysts for making polyolefins, including polypropylene, HDPE and LLDPE. The complexes disclosed by Nifant""ev do not have open architecture.
PCT Int. Appl. WO 01/53360 (Resconi et al.) discloses bridged [2,1-b]indenoindolyl complexes having open architecture and their use to produce substantially amorphous propylene-based polymers. Resconi teaches many open architecture complexes but none of them is a [1,2-b]indenoindolyl complex.
Pending Appl. Ser. No. 10/211,085 filed Aug. 2, 2002, now allowed, discloses a process for copolymerizing ethylene with at least one alpha-olefin selected from the group consisting of 1-butene, 1-hexene, and 1-octene in the presence of a catalyst system which comprises an activator and a silica-supported, indenoindolyl Group 4-6 transition metal complex having open architecture to produce an ethylene copolymer having a density less than about 0.910 g/cm3. While both [1,2-b] and [2,1-b]indenoindolyl complexes are disclosed, no comparative results between the two configurations are given nor is there any indication of improved activity. The advantage of using the open architecture complexes is stated to be the ability to incorporate comonomers in ethylene polymerizations to form low density polyethylene. Propylene is not disclosed as a monomer or as a comonomer.
Despite the considerable work done in this area, there is much that is not understood. There is a continued need for improved catalysts for propylene polymerizations. One need is improved activity. Improved activity lowers the cost of catalyst per kg of polymer produced. Also, since the catalyst is not removed from the polymer, improved activity lowers the amount of residual transition metal left in the polymer. High levels of residual transition metal can have deleterious effects such as poor aging properties or poor color retention. There is a continued need for high molecular weight elastomeric polypropylene for a variety of applications that require toughness, flexibility and elastic properties.
The invention is a process for the polymerization of propylene. The polymerization is done in the presence of a catalyst system which comprises an activator and a [1,2-b]indenoindolyl Group 4-6 transition metal complex having open architecture. Surprisingly, the [1,2-b]indenoindolyl complex is much more active than its counterpart [2,1-b]indenoindolyl complex in propylene polymerizations.
Catalyst systems useful for the process comprise an activator and a [1,2-b]indenoindolyl Group 4-6 transition metal complex having open architecture. More preferred complexes include a Group 4 transition metal such as titanium or zirconium.
xe2x80x9cIndenoindolylxe2x80x9d ligands are generated by deprotonating an indenoindole compound using a potent base. By xe2x80x9cindenoindole compound,xe2x80x9d we mean an organic compound that has both indole and indene rings. The five-membered rings from each are fused, i.e., they share two carbon atoms. The rings are fused such that the indole nitrogen and the only sp3-hybridized carbon on the indenyl ring are xe2x80x9ctransxe2x80x9d to each other. Such is the case in an indeno[1,2-b] ring system such as: 
The [2,1-b] complexes are excluded. For examples of [2,1-b] complexes, see PCT Int. Appl. WO 01/53360 (Resconi et al.).
The ring atoms can be unsubstituted or substituted with one or more groups such as alkyl, aryl, aralkyl, halogen, silyl, nitro, dialkylamino, diarylamino, alkoxy, aryloxy, thioether, or the like. Additional fused rings can be present, as long as an indenoindole moiety is present.
Numbering of indenoindoles follows IUPAC Rule A-22. The molecule is oriented as shown below, and numbering is done clockwise beginning with the ring at the uppermost right of the structure in a manner effective to give the lowest possible number to the heteroatom. Thus, 5,10-dihydro-indeno[1,2-b]indole is numbered as follows: 
For correct nomenclature and numbering of these ring systems, see the Ring Systems Handbook (1998), a publication of Chemical Abstracts Service, Ring Systems File II: RF 33986-RF 66391 at RF 58952 and 58955. (Other examples of correct numbering appear in PCT Int. Appl. WO 99/24446.)
Methods for making indenoindole compounds are well known. Suitable methods and compounds are disclosed, for example, in U.S. Pat. No. 6,232,260, the teachings of which are incorporated herein by reference, and references cited therein, including the method of Buu-Hoi and Xuong, J. Chem. Soc. (1952) 2225. Suitable procedures also appear in PCT Int. Appls. WO 99/24446 and WO 01/53360.
[1,2-b]Indenoindolyl complexes useful for the process of the invention have open architecture. By xe2x80x9copen architecture,xe2x80x9d we mean a complex having a fixed geometry that enables generation of a highly exposed active site when the catalyst is combined with an activator. The metal of the complex is pi-bonded to the indenyl Cp ring and is also sigma-bonded through two or more atoms to the indenyl methylene carbon. (In contrast, many of the bridged indenoindolyl complexes described in the literature have a transition metal that is pi-bonded to the indenyl Cp ring and pi-bonded to another Cp-like group. See, e.g., U.S. Pat. No. 6,232,260 or WO 99/24446).
Preferably, the metal is sigma-bonded to a heteroatom, i.e., oxygen, nitrogen, phosphorus, or sulfur; most preferably, the metal is sigma-bonded to nitrogen. The heteroatom is linked to the indenoindolyl group through a bridging group, which is preferably dialkylsilyl, diarylsilyl, methylene, ethylene, isopropylidene, diphenylmethylene, or the like. Particularly preferred bridging groups are dimethylsilyl, methylene, ethylene, and isopropylidene. The bridging group is covalently bonded to the indenyl methylene carbon.
In addition to the bridged [1,2-b]indenoindolyl ligand, the organometallic complex usually includes one or more labile anionic ligands such as halides, alkoxys, aryloxys, alkyls, alkaryls, aryls, dialkylaminos, or the like. Particularly preferred are halides, alkyls, and alkaryls (e.g., chloride, methyl, benzyl).
In a preferred process of the invention, the [1,2-b]indenoindolyl complex has the general structure: 
in which R1 is selected from the group consisting of C1-C30 hydrocarbyl, C1-C6 halocarbyl, C1-C30 halohydrocarbyl and trialkylsilyl; each R2 is independently selected from the group consisting of R1, H, F, Cl, Br and C1-C6 alkoxy; G is a divalent radical selected from the group consisting of hydrocarbyl and heteroatom containing alkylene radicals, diorgano silyl radicals, diorgano germanium radicals and diorgano tin radicals; L is a ligand that is covalently bonded to G and M; M is a Group 4 to 6 transition metal; each X is independently selected from the group consisting of halide, alkoxy, siloxy, alkylamino, and C1-C30 hydrocarbyl and n satisfies the valence of M. More preferably, M is a Group 4 transition metal, L is alkylamido, G is dialkysilyl, and X is halide or alkyl.
Exemplary organometallic complexes useful for the process of the invention: 
The complexes can be made by any suitable method; those skilled in the art will recognize a variety of acceptable synthetic strategies. The [1,2-b]indenoindolyl complexes can be made from the 1-indanone precursors in similar fashion as their counterpart [2,1-b]indenoindolyl complexes are made from the 2-indanone precursors. For synthesis of [2,1-b]indenoindolyl complexes, see especially PCT Int. Appl. WO 01/53360 for suitable routes. Often, the synthesis; begins with preparation of the desired [1,2-b]indenoindole compound from particular 1-indanone and arylhydrazine precursors. In one convenient approach, the indenoindole is deprotonated and reacted with dichlorodimethylsilane to attach a chlorodimethylsilyl group to the indenyl methylene carbon. Subsequent reaction with an amine or, more preferably, an alkali metal amide compound such as lithium tert-butylamide (from tert-butylamine and n-butyllithium), displaces chloride and gives the desired silylamine product. Double deprotonation and reaction with a transition metal source gives the target indenoindolyl metal complex having open architecture. A typical reaction sequence follows: 
A similar complex can be generated by amine elimination, which may or may not require heating, with a method explored by Professor Richard F. Jordan and coworkers at the University of Iowa: 
For additional examples of this approach to making organometallic complexes, see U.S. Pat. No. 5,495,035; J. Am. Chem. Soc. 118 (1996) 8024; and Organometallics 15 (1996) 4045.
Similar strategies can be used to make a wide variety of [1,2-b]indenoindolyl metal complexes having open architecture.
Any convenient source of the transition metal can be used to make the complex. As shown above, the transition metal source conveniently has labile ligands such as halide or dialkylamino groups that can be easily replaced by the indenoindolyl and amido anions of the bridged indenoindolyl ligand. Examples are halides (e.g., TiCl4, ZrCl4), alkoxides, amides, and the like.
Catalyst systems useful in the process include, in addition to the indenoindolyl metal complex, an activator. The activator helps to ionize the organometallic complex and activate the catalyst. Suitable activators are well known in the art. Examples include alumoxanes (methyl alumoxane (MAO), PMAO, ethyl alumoxane, diisobutyl alumoxane), alkylaluminum compounds (triethylal uminum, diethyl aluminum chloride, trimethylaluminum, triisobutyl aluminum), and the like. Suitable activators include acid salts that contain non-nucleophilic anions. These compounds generally consist of bulky ligands attached to boron or aluminum. Examples include lithium tetrakis(pentafluorophenyl)borate, lithium tetrakis(pentafluorophenyl)aluminate, anilinium tetrakis(penta-fluorophenyl)borate, and the like. Suitable activators also include organoboranes, which include boron and one or more alkyl, aryl, or aralkyl groups. Suitable activators include substituted and unsubstituted trialkyl and triarylboranes such as tris(pentafluorophenyl)borane, triphenylborane, tri-n-octylborane, and the like. These and other suitable boron-containing activators are described in U.S. Pat. Nos. 5,153,157, 5,198,401, and 5,241,025, the teachings of which are incorporated herein by reference. Suitable activators also include aluminoboronatesxe2x80x94reaction products of alkyl aluminum compounds and organoboronic acidsxe2x80x94as described in U.S. Pat. Nos. 5,414,180 and 5,648,440, the teachings of which are incorporated herein by reference. Alumoxane activators, such as MAO, are preferred.
The optimum amount of activator needed relative to the amount of organometallic complex depends on many factors, including the nature of the complex and activator, the desired reaction rate, the kind of polyolefin product, the reaction: conditions, and other factors. Generally, however, when the activator is an alumoxane or an alkyl aluminum compound, the amount used will be within the range of about 0.01 to about 5000 moles, preferably from about 10 to about 500 moles, and more preferably from about 10 to about 200 moles, of aluminum per mole of transition metal, M. When the activator is an organoborane or an ionic borate or aluminate, the amount used will be within the range of about 0.01 to about 5000 moles, preferably from about 0.1 to about 500 moles, of activator per mole of M. The activator can be combined with the complex and added to the reactor as a mixture, or the components can be added to the reactor separately.
Optionally, the complex is immobilized on a support. The support is preferably a porous material such as inorganic oxides and chlorides, and organic polymer resins. Preferred inorganic oxides include oxides of Group 2, 3, 4, 5, 13, or 14 elements. Preferred supports include silica, alumina, silica-aluminas, magnesias, titania, zirconia, magnesium chloride, and crosslinked polystyrene. Most preferred is silica. The silica is preferably treated thermally, chemically, or both prior to use to reduce the concentration of surface hydroxyl groups. Thermal treatment consists of heating (or xe2x80x9ccalciningxe2x80x9d) the silica in a dry atmosphere at elevated temperature, preferably, greater than about 100xc2x0 C., and more preferably from about 150 to about 600xc2x0 C., prior to use. A variety of different chemical treatments can be used, including reaction with organo-aluminum, -magnesium, -silicon, or -boron compounds. See, for example, the techniques described in U.S. Pat. No. 6,211,311, the teachings of which are incorporated herein by reference.
Many types of polymerization processes can be used. The process can be practiced in the gas phase, bulk, solution, or slurry. The polymerization can be performed over a wide temperature range. Generally, lower temperatures give higher molecular weight and longer catalyst lifetimes. However, since the polymerization is exothermic, lower temperatures are more difficult and costly to achieve. A balance must be struck between these two factors. Preferably, the temperature is within the range of about 0xc2x0 C. to about 150xc2x0 C. A more preferred range is from about 20xc2x0 C. to about 90xc2x0 C.
Catalyst concentrations used for the olefin polymerization depend on many factors. Preferably, however, the concentration ranges from about 0.01 micromoles per liter to about 100 micromoles per liter. Polymerization times depend on the type of process, the catalyst concentration, and other factors. Generally, polymerizations are complete within several seconds to several hours.
Polypropylene prepared by this process is elastomeric. One indication that the polypropylene is elastomeric is the tacticity of the polypropylene prepared by the process. The tacticity of a polymer affects its properties. The term xe2x80x9ctacticityxe2x80x9d refers to the stereochemical configuration of the polymer. For example, adjacent monomer units can have either like or opposite configuration. If all monomer units have like configuration, the polymer is xe2x80x9cisotactic.xe2x80x9d If adjacent monomer units have opposite configuration and this alternating configuration continues along the entire polymer chain, the polymer is xe2x80x9csyndiotactic.xe2x80x9d If the configuration of monomer units is random, the polymer is xe2x80x9catactic.xe2x80x9d When two contiguous monomer units, a xe2x80x9cdiad,xe2x80x9d have the same configuration, the diad is called isotactic or xe2x80x9cmesoxe2x80x9d (m). When the monomer units have opposite configuration, the diad is called xe2x80x9cracemicxe2x80x9d (r). For three adjacent monomer units, a xe2x80x9ctriad,xe2x80x9d there are three possibilities. If the three adjacent monomer units have the same configuration, the triad is designated mm. An rr triad has the middle monomer unit having an opposite configuration from either neighbor. If two adjacent monomer units have the same configuration and it is different from the third monomer, the triad is designated as having mr tacticity. The configuration can be determined by 13C nuclear magnetic resonance spectroscopy as described in Macromolecules 8 687 (1975) and in Macromolecules 6 925 (1973) and references cited therein. For more information on polymer stereochemistry, see G. Odian, Principles of Polymerization, 2nd edition, pages 568-580 (1981).
The configuration of the monomer units affects the polymer properties. The polypropylene made by the process of the invention is characterized in that it is neither highly isotactic nor highly syndiotactic. This tacticity is an indication of elastomeric properties.
The polypropylene has high molecular weight and low polydispersity. The Mw and polydispersity (Mw/Mn) can be measured by gel permeation chromatography and affect polymer properties such as elasticity. Generally, the elastic properties such as tensile set and stress recovery improve with increasing molecular weight. The Mw is typically greater than 100,000, preferably between 200,000 and 1,500,000 and more preferably between 300,000 and 1,200,000. The polydispersity is typically below 5.0, preferably between 2 and 4 and most preferably between 2.5 and 3.5.
The following examples merely illustrate the invention. Those skilled in the art will recognize many variations that are within the spirit of the invention and scope of the claims.